1. Field of the Invention
The present invention relates to an image forming apparatus and more particularly to a device for applying a lubricant to an image carrier included in an image forming apparatus.
2. Discussion of the Background
An image forming apparatus of the type sequentially executing charging, exposure, development and image transfer is extensively implemented as, e.g., a digital or an analog copier, laser printer or facsimile apparatus. This type of apparatus forms a latent image on a photoconductive element by charging and exposure and then develops the latent image to thereby form a corresponding toner image. The toner image is transferred from the photoconductive element to a paper or similar recording medium and then fixed on the recording medium.
The toner image is transferred from the photoconductive element to a recording medium either directly or by way of an intermediate transfer belt or similar intermediate transfer medium. The photoconductive element and intermediate transfer medium will be collectively referred to as an image carrier because each of them temporarily carries the toner image thereon.
Generally, not the entire toner image is transferred from the image carrier to a recording medium, i.e., part of toner remains on the image carrier after image transfer. It is therefore necessary to remove the toner left on the image carrier after image transfer. To meet this requirement, a cleaning blade or a cleaning brush is usually mechanically held in sliding contact with the surface of the image carrier. However, the cleaning blade and cleaning brush each cause the surface of the image carrier to wear. When the image carrier is implemented by a photoconductive element, the above wear deteriorates the characteristics of the element and thereby obstructs the formation of an expected latent image. When it comes to an intermediate transfer medium, the wear results in defective image transfer. To protect the image carrier from wear ascribable to cleaning, it is effective to reduce the coefficient of friction of the surface of the image carrier, as well known in the art. In light of this, it has been customary to apply a lubricant to the surface of the image carrier.
A conventional lubricant applying device includes a brush roller rotatable in a preselected direction while being pressed against the image carrier by a preselected pressure in the widthwise direction of the image carrier. A plurality of springs are used to press the lubricant against the brush roller with uniform pressure. The lubricant is sequentially consumed as it is repeatedly shaved off and applied to the image carrier. Although the lubricant decreases in thickness, the lubricant can be used up without any waste because it is constantly pressed against the brush roller by the springs.
However, when the lubricant is new and therefore thick, the lubricant is pressed against the brush roller by a pressure great enough for it to bite into the brush roller, causing the brush roller to noticeably deform. Particularly, when the image forming apparatus is left unused over a long period of time, e.g., at weekend or during vacation, the deformation of the brush roller ascribable to the bite of the lubricant remains. As a result, when the apparatus is used after a long interval, the brush roller fails to smoothly apply the lubricant to the image carrier until it restores its original configuration. This aggravates the wear of the image carrier. Further, the springs need an extra space to be accommodated and increase the number of parts that would obstruct the low cost, compact construction of the lubricant applying device.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 7-334058 and 8-248776 and Japanese Patent Publication No. 7-120114.